Guys,
I will try to share as much experience gained as possible. Finally I managed to connect the 3090 ti to my p870tm-g using a m.2 to pcie converter. I connected the converter to the only m.2 that I had available, it is the one used for optane disks. I am using my screen connected directly to the 3090 ti. I got this adapter but I am planning to change it for the k43sg because is newer and it supports pcie 4 https://www.aliexpress.us/item/3256803093134104.html?aff_fcid=eb2bd4815b5e447d8e8ae81dbaa86663-1689688648425-04964-_DDbI7T
I didn't have to unlock the bios, but I had to disable the ACPI. I would have never found that if it wasn't for @MR007RM thank you man, you are the best 🙂
During that path @Tenoroon (1 million thanks) shared with me this link where you can get the latest Dsanke bios, the one using an external programmer as well as the one where you only need a flash drive and several steps described inside. https://files.catbox.moe/b9081g.zip
I even tried to get some help from Eurocom to get the unlocked bios, which they clearly have, but they wanted to charge me around $100 for that. Please buy used gear from Eurocom, they don't deserve to have good customers from this community.
Thank you @MR007RM and @Tenoroon for your invaluable help guys!!! You rock!!! Also thank you @ViktorV, @Developer79, @Scruffy, and @runix18 for so many advices to solve so many mysteries 🙂
I have a question that maybe you might help me solving: Do you know how can I make to enable both the 3090 ti using the converter, as well as the 1080 mxm installed in the laptop simultaneously? I know that in desktops you can do it, and our board is so similar that maybe that could work. It would be great to have both cards enabled, so I can plug more displays to work. Right now only the one connected to the 3090 ti is working, but I'd love to have also the one connected to the mini displayport.
Thank you guys!!!!!!!!