Well I have used the apt source list, vivid 15.04 host and it installs OK for me (on 64-bits). Here is the output from 5 minutes ago:
id@emachines-e520:~/docker-images$ tail -2 /etc/apt/sources.list
deb
https://dl.bintray.com/tvheadend/ubuntu master main
# deb-src https://dl.bintray.com/tvheadend/ubuntu master main
id@emachines-e520:~/docker-images$ sudo apt-get update -qqy
id@emachines-e520:~/docker-images$ apt search tvheadend
Sorting... Done
Full Text Search... Done
kodi-pvr-hts/now 2.1.7-1~vivid amd64 [installed,local]
TVHeadEnd PVR for Kodi
tvheadend/master 4.1-166~g4d72204~trusty amd64 [residual-config]
Tvheadend
tvheadend-dbg/master 4.1-166~g4d72204~trusty amd64
Debug symbols for Tvheadend
xbmc-pvr-tvheadend-hts/vivid 13.0+git20140512+g91cc731+dfsg1-1 amd64
XBMC PVR Addon TvHeadend Hts
id@emachines-e520:~/docker-images$ sudo apt-get install tvheadend
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following extra packages will be installed:
libdvbcsa1 liburiparser1
The following NEW packages will be installed
libdvbcsa1 liburiparser1 tvheadend
0 to upgrade, 3 to newly install, 0 to remove and 3 not to upgrade.
Need to get 9,582 kB of archives.
After this operation, 25.0 MB of additional disk space will be used.
Do you want to continue? [Y/n] Y
Get:1
http://gb.archive.ubuntu.com/ubuntu/ vivid/universe libdvbcsa1 amd64 1.1.0-2 [32.7 kB]
Get:2
http://gb.archive.ubuntu.com/ubuntu/ vivid/universe liburiparser1 amd64 0.8.0.1-2 [36.6 kB]
Get:3
https://dl.bintray.com/tvheadend/ubuntu/ master/main tvheadend amd64 4.1-166~g4d72204~trusty [9,513 kB]
Fetched 9,582 kB in 24s (395 kB/s)
Preconfiguring packages ...
Selecting previously unselected package libdvbcsa1:amd64.
(Reading database ... 258378 files and directories currently installed.)
Preparing to unpack .../libdvbcsa1_1.1.0-2_amd64.deb ...
Unpacking libdvbcsa1:amd64 (1.1.0-2) ...
Selecting previously unselected package liburiparser1.
Preparing to unpack .../liburiparser1_0.8.0.1-2_amd64.deb ...
Unpacking liburiparser1 (0.8.0.1-2) ...
Selecting previously unselected package tvheadend.
Preparing to unpack .../tvheadend_4.1-166~g4d72204~trusty_amd64.deb ...
Unpacking tvheadend (4.1-166~g4d72204~trusty) ...
Processing triggers for man-db (2.7.0.2-5) ...
Processing triggers for ureadahead (0.100.0-19) ...
ureadahead will be reprofiled on next reboot
Processing triggers for systemd (219-7ubuntu5) ...
Setting up libdvbcsa1:amd64 (1.1.0-2) ...
Setting up liburiparser1 (0.8.0.1-2) ...
Setting up tvheadend (4.1-166~g4d72204~trusty) ...
insserv: warning: script 'K01-grub-reboot-linux' missing LSB tags and overrides
Processing triggers for libc-bin (2.21-0ubuntu4) ...
id@emachines-e520:~/docker-images$ tvheadend --version
tvheadend: version 4.1-166~g4d72204
id@emachines-e520:~/docker-images$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 15.04
Release: 15.04
Codename: vivid
id@emachines-e520:~/docker-images$ uname -m
x86_64
id@emachines-e520:~/docker-images$
I also tested at runtime (with my existing tvheadend config folder) on 15.04 host - and it worked OK. The tvheadend server would start normally. My tv channels would play correctly in HTSP client. Everything seemed normal.
So you can see: it's not so bad. The distro field - it doesn't matter for tvheadend. (at least for the time being everything is OK, it is no need to worry).
Also:
* You mentioned about the ARM builds.
Actually there are some few guys making ARM builds of the new version 4.0.x stable. One guy is making a Synology ARM pkg (hopefully to eventually become official on synology), another person is making good package for Arch linux. Which is official in the Arch linux packman pkg repository. Another person is compiling natively for rpi (on an rpi).
It's just that we don't know yet how to make cross-compile builds for ARM. On ubuntu 64-bit Intel host (to make ubuntu ARM .deb).