Thanks for your detailed answers, which I really appreciate.
I already have a ChromeCast 3 dongle which I used for an Android phone, and found out yesterday, that to use Chromium on PMOS has become easy. On my Windows PC, it was also very easy to mirror the screen over a ChromeCast to HDMI. I currently have VNC server connection between PinePhone and PC, but I think a WIFI to HDMI solution would be better. If I would buy a new device, I would prefer the Miracast standard, although I don t know whether desktop mirroring is as easy as with the Chrome browser.
I am also positive now about LibreOffice on the PinePhone. Jacob Crume, a Robotics student in New Zealand used linux-based PinePhone daily for a year:
https://news.itsfoss.com/pinephone-review/
He used four desktop environment, Plasma Mobile, Phosh and Lomiri, he spent roughly four months with each environment.
He was surprised at how capable the PinePhone was as a laptop. He said he often found myself editing documents in LibreOffice.
That is good news.