Had a play tonight - using my Samsung tablet (SM-T580, Android 9) and OnePlus 5T (Android 9), with a variety of input devices:
Switch Pro, DS4, Xbox One (Bluetooth) and Steam Controller, plus an old Logitech MX5500 Bluetooth mouse and a cheap miniature keyboard.
I had a selection of games across a few platforms available (Borderlands 3 on Epic, Hellblade: Senua's Sacrifice and Warhammer 40K: Inquisitor on Steam, Division 2 on Uplay and Anthem on Origin).
I also used the brilliant
Power A Moga clip with my phone and the XBone controller, which although heavy, was by far the most mobile/portable solution.
Tried Borderlands 3 on the tablet, using M&K (horribly laggy and unresponsive - but could be due to the age of the M&K), then the Xbox controller (left stick kept drifting unless I clicked L3 to stop and movement was extremely slow).
DS4 worked great, albeit only recognised as a 360 controller with incorrect button mapping - I believe Android 10/Q fixes this, so I'll update my Tablet tomorrow and give it a try.
Switch Pro was also slow - I expect I'm missing a setting to increase sensitivity.
I also had a try with Steam Big Picture mode and the Steam Controller worked far better.
First impressions were slightly disappointing, but promising - I need to have a more thorough play with controller settings or source a Bluetooth mouse/keyboard set that isn't from nearly two decades ago.
I've also found out that Android 10 allows PS4 remote play with the DS4 connected to the tablet, so it looks like my opportunity to play is no longer restricted by when The Wife lets me access the lounge TV.