@allllo, Hi, welcome to the forum, please read How to get the best out of this forum.
"The actual version of the 2.9" b/w e-paper board from Waveshare is not supported by GxEPD2." Has been falsified by @vanilla_chief .
I don't have that board, and nobody had confirmed which panel this board actually uses.
Newbies can't use this board with GxEPD2, because they don't read the remarks in README.md concerning "clever" reset circuit and pull-down on CS.
And they are not able to provide enough information for me to help them. E.g. processor used.
The best solution is to tell Waveshare they should send me a free sample, so I could check.
Jean-Marc