This is very unlikely the issue. Whether or not you start HTTPS, the local connection - the steaming from tablo to your browser is not either way. That’s part of the new issue with Chrome.
Under Privacy and Security you have an option to NOT have Firefox add it… while virtually most all web sites now will redirect you. I turned it off, makes it easier to access my router by name for one. There may still be a site or two without an SSL certificate which I still need/want to visit. I suppose I could/should add an exception.
If you really want to dig into things… about:profiles and restart with Add-Ons Disabled OR Help > Troubleshoot Mode (this used to be called safe mode)
How different are you Firefox configurations between devices? Least ideal choice, copy your working profile to your other systems (although I’ve done this, it’s not something to recommend). Firefox has a sync facility (me, I’ve signed in, sync’d and signed out) It’s a bit easier have different systems set up very similar.
Yea, I have a Windows 10 PC which I have little to no use for but it’s nice to have the same Firefox setup if/when I do use it.
Is there a difference how either of these systems connect to your network?
“securing the browser” ?? in what ways was it insecure? Had you secured anything on the network level? (proxy, vpn)?