Attempting to install Tvheadend (focal) from source files on Tvheadend Wiki--APT Repositories. Still assuming that 'focal' is the correct version for LinuxMint 20.3.
1. sudo apt-get -y install coreutils wget apt-transport-https lsb-release ca-certificates
All good
2. sudo wget -qO-
https://doozer.io/keys/tvheadend/tvheadend/pgp | sudo apt-key add -
returns value of 'OK'
3. sudo sh -c 'echo "deb
https://apt.tvheadend.org/unstable focal main" | tee -a /etc/apt/sources.list.d/tvheadend.list'
returns value of 'deb
https://apt.tvheadend.org/unstable focal main'
4. sudo apt-get update
returns...
Ign:1
https://apt.tvheadend.org/unstable focal InRelease
Hit:2
https://apt.tvheadend.org/unstable focal Release
Ign:4
http://packages.linuxmint.com una InRelease
Hit:5
http://packages.linuxmint.com una Release
Hit:6
http://archive.canonical.com/ubuntu focal InRelease
Hit:8
http://security.ubuntu.com/ubuntu focal-security InRelease
Hit:9
http://archive.ubuntu.com/ubuntu focal InRelease
Hit:10
http://archive.ubuntu.com/ubuntu focal-updates InRelease
Hit:11
http://archive.ubuntu.com/ubuntu focal-backports InRelease
Reading package lists... Done
W: Target Packages (main/binary-amd64/Packages) is configured multiple times in /etc/apt/sources.list.d/additional-repositories.list:1 and /etc/apt/sources.list.d/tvheadend.list:1
W: Target Packages (main/binary-i386/Packages) is configured multiple times in /etc/apt/sources.list.d/additional-repositories.list:1 and /etc/apt/sources.list.d/tvheadend.list:1
W: Target Packages (main/binary-all/Packages) is configured multiple times in /etc/apt/sources.list.d/additional-repositories.list:1 and /etc/apt/sources.list.d/tvheadend.list:1
W: Target Translations (main/i18n/Translation-en_US) is configured multiple times in /etc/apt/sources.list.d/additional-repositories.list:1 and /etc/apt/sources.list.d/tvheadend.list:1
W: Target Translations (main/i18n/Translation-en) is configured multiple times in /etc/apt/sources.list.d/additional-repositories.list:1 and /etc/apt/sources.list.d/tvheadend.list:1
W: Target DEP-11 (main/dep11/Components-amd64.yml) is configured multiple times in /etc/apt/sources.list.d/additional-repositories.list:1 and /etc/apt/sources.list.d/tvheadend.list:1
W: Target DEP-11 (main/dep11/Components-all.yml) is configured multiple times in /etc/apt/sources.list.d/additional-repositories.list:1 and /etc/apt/sources.list.d/tvheadend.list:1
W: Target CNF (main/cnf/Commands-amd64) is configured multiple times in /etc/apt/sources.list.d/additional-repositories.list:1 and /etc/apt/sources.list.d/tvheadend.list:1
W: Target CNF (main/cnf/Commands-all) is configured multiple times in /etc/apt/sources.list.d/additional-repositories.list:1 and /etc/apt/sources.list.d/tvheadend.list:1
W: Target Packages (main/binary-amd64/Packages) is configured multiple times in /etc/apt/sources.list.d/additional-repositories.list:1 and /etc/apt/sources.list.d/tvheadend.list:2
W: Target Packages (main/binary-i386/Packages) is configured multiple times in /etc/apt/sources.list.d/additional-repositories.list:1 and /etc/apt/sources.list.d/tvheadend.list:2
W: Target Packages (main/binary-all/Packages) is configured multiple times in /etc/apt/sources.list.d/additional-repositories.list:1 and /etc/apt/sources.list.d/tvheadend.list:2
W: Target Translations (main/i18n/Translation-en_US) is configured multiple times in /etc/apt/sources.list.d/additional-repositories.list:1 and /etc/apt/sources.list.d/tvheadend.list:2
W: Target Translations (main/i18n/Translation-en) is configured multiple times in /etc/apt/sources.list.d/additional-repositories.list:1 and /etc/apt/sources.list.d/tvheadend.list:2
W: Target DEP-11 (main/dep11/Components-amd64.yml) is configured multiple times in /etc/apt/sources.list.d/additional-repositories.list:1 and /etc/apt/sources.list.d/tvheadend.list:2
W: Target DEP-11 (main/dep11/Components-all.yml) is configured multiple times in /etc/apt/sources.list.d/additional-repositories.list:1 and /etc/apt/sources.list.d/tvheadend.list:2
W: Target CNF (main/cnf/Commands-amd64) is configured multiple times in /etc/apt/sources.list.d/additional-repositories.list:1 and /etc/apt/sources.list.d/tvheadend.list:2
W: Target CNF (main/cnf/Commands-all) is configured multiple times in /etc/apt/sources.list.d/additional-repositories.list:1 and /etc/apt/sources.list.d/tvheadend.list:2
N: Skipping acquire of configured file 'main/binary-i386/Packages' as repository '
https://apt.tvheadend.org/unstable focal InRelease' doesn't support architecture 'i386'
W: Target Packages (main/binary-amd64/Packages) is configured multiple times in /etc/apt/sources.list.d/additional-repositories.list:1 and /etc/apt/sources.list.d/tvheadend.list:1
W: Target Packages (main/binary-i386/Packages) is configured multiple times in /etc/apt/sources.list.d/additional-repositories.list:1 and /etc/apt/sources.list.d/tvheadend.list:1
W: Target Packages (main/binary-all/Packages) is configured multiple times in /etc/apt/sources.list.d/additional-repositories.list:1 and /etc/apt/sources.list.d/tvheadend.list:1
W: Target Translations (main/i18n/Translation-en_US) is configured multiple times in /etc/apt/sources.list.d/additional-repositories.list:1 and /etc/apt/sources.list.d/tvheadend.list:1
W: Target Translations (main/i18n/Translation-en) is configured multiple times in /etc/apt/sources.list.d/additional-repositories.list:1 and /etc/apt/sources.list.d/tvheadend.list:1
W: Target DEP-11 (main/dep11/Components-amd64.yml) is configured multiple times in /etc/apt/sources.list.d/additional-repositories.list:1 and /etc/apt/sources.list.d/tvheadend.list:1
W: Target DEP-11 (main/dep11/Components-all.yml) is configured multiple times in /etc/apt/sources.list.d/additional-repositories.list:1 and /etc/apt/sources.list.d/tvheadend.list:1
W: Target CNF (main/cnf/Commands-amd64) is configured multiple times in /etc/apt/sources.list.d/additional-repositories.list:1 and /etc/apt/sources.list.d/tvheadend.list:1
W: Target CNF (main/cnf/Commands-all) is configured multiple times in /etc/apt/sources.list.d/additional-repositories.list:1 and /etc/apt/sources.list.d/tvheadend.list:1
W: Target Packages (main/binary-amd64/Packages) is configured multiple times in /etc/apt/sources.list.d/additional-repositories.list:1 and /etc/apt/sources.list.d/tvheadend.list:2
W: Target Packages (main/binary-i386/Packages) is configured multiple times in /etc/apt/sources.list.d/additional-repositories.list:1 and /etc/apt/sources.list.d/tvheadend.list:2
W: Target Packages (main/binary-all/Packages) is configured multiple times in /etc/apt/sources.list.d/additional-repositories.list:1 and /etc/apt/sources.list.d/tvheadend.list:2
W: Target Translations (main/i18n/Translation-en_US) is configured multiple times in /etc/apt/sources.list.d/additional-repositories.list:1 and /etc/apt/sources.list.d/tvheadend.list:2
W: Target Translations (main/i18n/Translation-en) is configured multiple times in /etc/apt/sources.list.d/additional-repositories.list:1 and /etc/apt/sources.list.d/tvheadend.list:2
W: Target DEP-11 (main/dep11/Components-amd64.yml) is configured multiple times in /etc/apt/sources.list.d/additional-repositories.list:1 and /etc/apt/sources.list.d/tvheadend.list:2
W: Target DEP-11 (main/dep11/Components-all.yml) is configured multiple times in /etc/apt/sources.list.d/additional-repositories.list:1 and /etc/apt/sources.list.d/tvheadend.list:2
W: Target CNF (main/cnf/Commands-amd64) is configured multiple times in /etc/apt/sources.list.d/additional-repositories.list:1 and /etc/apt/sources.list.d/tvheadend.list:2
W: Target CNF (main/cnf/Commands-all) is configured multiple times in /etc/apt/sources.list.d/additional-repositories.list:1 and /etc/apt/sources.list.d/tvheadend.list:2
And,
4. sudo apt-get install tvheadend
returns...
Reading package lists... Done
Building dependency tree
Reading state information... Done
tvheadend is already the newest version (4.3-1995~g1d0b5e89d~focal).
0 upgraded, 0 newly installed, 0 to remove and 34 not upgraded.
This appears to have installed properly. I rebooted my system and attempted to initiate Tvheadend configuration (http://localhost:9981), and received a request to logon ??? No matter what I seem to enter, I receive a '403 Forbidden' screen. So, not sure what my next move is.