I'm thinking about using old computers and/or cell phones for home theater PC applications. Since having a remote control is kind of important in this house, we need something for screen sharing to navigate web pages for viewing and to select "full screen" to put the web's video on the full tv screen. Or perhaps a remote control program might be more useful? Also some of the old computers do not have bluetooth so wifi might be a handy option depending on what we use.

Do you have suggestions for screen sharing/remote control apps to use if I have Ubuntu Touch onto an old phone for this purpose? Or is another distro for this? Thanks!

Sorry, but for me using a remote control is better than anything with touchscreen. (In case the computer has no IR receiver there is Flirc, fully programmable to any spare remote you may have.) Remote control with buttons I do not need to look at when operating, just feel it with my fingers, while looking at TV screen.
And old computers are really not good for anything, if they are really old. For a high definition media player you need hardware decoding for H.264, HEVC, VP9. Old computers can't do it.

Things are new enough. My 2013 computer can see any video file or web site I'd need except it can't do bluetooth. I suppose that hampers it in a way that might need either a hardware dedicated remote or wifi control or screen sharing to a cell phone.

My old prepaid cell phones are so cheap I buy new ones every year rather than pay for a subscription (service+phone is cheaper than an extra year of service, which is fine for me) and they can do the same but WITH Bluetooth. I found out linux is kind of a no-go for the cheap phones I use so that makes things more difficult. Yes a real remote and purpose-built HTPC is better but an immediate free download is cheaper and faster than paying for a mail order remote.

Judging by the few responses on the thread, there aren't a lot of people on this forum who use old tech for that purpose. I'll check out the Flirc when I make a decision on HTPC hard. Thank you for the tip Emerson.

I think plex had a way to use a phone to control htpc. Not sure.

Please specify: do you mean actual dumb cell phones, or smartphones?

If the latter: of course Android apps exist that can do (something like) what you want.

And of course Linux software exists to make your 2013 laptop do what you want (provided it has the hardware required).

The whole HTPC remote thing is no longer on a time-crunch (or necessary immediately) but I am curious about it.

I'll have to check out Plex, thank you Jefro.

ondoho: I don't know exactly what constitutes a "smart" phone vs not, it's an LG running android on a touchscreen that can stream from YouTube, shoot video, and sold for $50 this year. It wasn't on the list to run Ubuntu Touch though. The remote control aspect may be what interests me more even than the HTPC at this point. Kubi seems like it might do the HTPC job.

^ any version of Android, that's definitely a "smartphone", whatever your personal definition of "smart" may be.
A cell phone is a superset (a smartphone is also a cell phone) but in 2021, using that term (esp. combined with "old") is most likely a conscious decision to distinguish something like this from a smartphone.

I wasn't that "conscious"/specific about phones ondoho but seeing pics of the classic phones at the link was fun.