Bit late to this thread but thought I'd add my own experiences with
18.04 in case it helps others.
I migrated from 16.04 a few weeks ago. For historical reason I build
(built) tvheadend from source but used kodi + hts pvr from the xbmc
ppa.
The last commit I built from was (4.3-262~g)8011a8c back in July 2017.
I'm currently using a Geniatech T230 I got from Amazon. It took a
while to find some firmware that worked but, after trying pretty much
every candidate I could find "out there", I found one that worked and
my setup has worked well and was really stable.
When I moved to 18.04 I tried to build the 8011a8c commit but got
problems.
I decide to focus on building the latest commit cited on the home
page - (4.3-1252~g)595fl174f - which didn't prove too hard.
That's the version I'm using right. Originally I used kodi + pvr from
the Ubuntu repos but, literally just now, switched to the xbmc ppa. (I
found initially that the Ubuntu version was more stable that the ppa
version.)
I'm using the same firmware as I used in 16.04 but have no idea as to
whether it is entirely suitable for 18.04.
The 18.04 combo has not been stable. These points reflect my
experience while using the Ubuntu repos:
I see many, many more checksum errors reported by tvheadend and kodi
often could not "tune in" to channels consistently
kodi frequently crashed immediately when I started it, I'd just retry
until it started sucessfully.
I noticed that if Kodi is running and I start playing some music,
frequently everything freezes for ~10seconds before continuing ok. (I
know there were issues with audio on 18.04; some alsa config files
were recently updated.)
I use LibreElec on a Pi talking to my 18.04 system and sometimes it
just can not tune in at all, let alone maintain a stable connection.
Its to be expected that 18.04 will not be as stable yet as 16.04: I
see crashes of e.g Chrome, nautilus frequently so I've held off trying
to dig deeper into specific tvheadend / kodi issues.
Happy to clarify / expand (where I can) if of any interest.