Thanks to all that considered my problem and took the time to reply
For the benefit of any other newbies, I learned indirectly from the above comments that I had in my ignorance installed a Snap (package?) version. I hadn't heard of Snap until now as I had always used Mint which doesn't install Snap by default it seems (good IMHO just another thing to learn)
I am now using linux Mint and installed TVH via the command line following the instructions here
https://tvheadend.org/projects/tvheadend/wiki/AptRepositories
Starting from Usage and substituting
$(lsbrelease -sc)_ with
focal - focal being the Ubuntu package base for my Mint version
This resulted in installation of version
4.2.8-36~g5bdcfd8ac and I am able to understand (mostly !) where TVH is/can place it's recordings