I'm adding a 256gb Corsair M.2 SSD to my semi-aging (no M.2 slots) motherboard, apparently it is compatible with the mobo to do so with the pci-e 4.0 x16 adapter I bought with it, although I'm stopgapped at pci-e 2.0, will 20.04.4 LTS see it?

I've seen how nvme (m.2 or the other kind that needs to be connected with a sata wire to the mobo additonally, ubuntu/debian sees normal hard drives as /dev/sdx , I'm also going to be adding a 800mb/sec regular 2.5 inch 1TB SSD (cheaper, but it was worth it, bought it on dell's website, they sell third party hardware somehow, real cheap), i've seen that the m.2 ssd will be seen as /dev/nvme1, will it be naming the regular SSD's^^this one, WD Blue 1TB NAND SSD, as /dev/ssd1 or it's going to be sdb(x) like the 2 other regular mechanic drives connected to this desktop (one internal, one on an usb 3.0/eSATA...haven't installed the eSATA III input to that desktop yet since I'm pretty sure usb 3.0 is faster or about the same as eSATA III.

I know I'm late to the party, believe me, I've been careless for a while, I guess it happens with linux, when you know how to deal with it (have a decade+ experience with debian and sub-debian flavours such as the typical ubuntu or now ubuntu mate since Linux Mint has kernel update issues (they're always behind) and I always found it buggier than just using Ubuntu MATE, I love the GUI, that's about it), hardware tends to work and degrade a lot less when not using Windows IME, so I'm getting into SSD's now....at least now it seems worth it, with the M.2 direct to motherboard drives.

Now for the main question : Apparently the exact adapter I bought works just fine to make nvme drives work with my motherboard, so I'm not worried about this too much, what bothers me is that I hear that, if I was to be using two video adapters in CrossFire, the 2 units would lose some of their power, making it difficult to have it be worth it to have 2 video adapters, when I bought that Radeon HD 7870 it came with the CrossFire adapter but I never bothered, I play Shadowrun Returns and its sequels which are Linux compatible and thats about it. But I hear that if I am to put the m.2 ssd in that second pci-e x16 slot, it would slow down my video adapter on the other one.

Is it something that would be really noticeable or just something video aficionados and maniacs with 1k worth video cards would not tolerate? It would likely be where I will make a partition clone of the one where MATE 20.04.4 LTS is and paste it to that nvme m.2 drive, even if my motherboard is getting a bit old, with pci-e 2.0, it will be stopgapped at 2000MB/sec but that's still much faster than the 380 something it's at right now on the mechanical drive that's 6gb/s SATA, but if it messes with the video adapter too much, I'm hesitating on going that route and might just clone the partition but put it on the regular SSD I will also be installing, it gets to 830mb/sec, decent enough I imagine.

Lots of text I know sorry, I might clean this up a little tomorrow, I should be sleeping right now :sleeping_bed: :zzz:

I'm not sure what your are asking? It appears you might have answered your own question. You might want to list the motherboard specs (i.e., make and model number). In my past research, I found that nvme m.2 drives/risers don't work with certain aged boards.