While your question has already been answered, i would like to add
Pcie is very compatible, its both backwards and forewards compatible (sure it wont be as fast but it will work)
Pretty sure you should be able to do something like takeing a rtx 5090 and a dremmel and puting it in a gen 1 pcie x1 slot
(Wether you cut the back of the x1 slot or cut the rtx 5090 is up for reader interpritation)
Lets make a compromise
Deadnt