Did you consider the Planet Computers' Gemini? Martin Riddiford who designed the keyboards for the Psion 3 and 5 series did the magic again.

https://www.www3.planetcom.co.uk/gemini-pda

Got mine in 2017 from their Indiegogo launch and as a previous 5mx user in the 90s how could I not?

Sadly they never updated the OS so it's not really much use now. The inability to make some android apps flip to landscape was also a little frustrating.