I believe trilobite@lemdro.id meant a mini-pc to flash a type of AndroidTV like Linux OS on it.
Like a Raspi 0 with IR remote and a tv OS.

Google Chromecast AndroidTV (what I use for Jellyfin) or FireTV stick (not sure about support).

Too much responaibility in case of downtime. I will rather pay.

Movies on the other hand…

Wish you the best of luck!

I think this is the best I could find:
https://www.xcase.co.uk/products/asus-ipmi-expansion-card-w-dedicated-ethernet-controller-vga-port-pcie-3-0-x1-aspeed-ast2600a3-oem-packaging

https://www.newegg.com/en-labs-pcifanco8spr-metal-fan-speed-controller/p/376-0067-00009

But those two are not really what you are probably looking for.
I think you last and least janky solution outside of designing your own PCB would be a PWM to USB adapter.

Besides that, I saw some fan Hubs powered by Molex. If you have any sata or molex power in thr back of the server it might fit there and look more proper.
Remember though: If the airflow of the server fans are too great on the fan it could turn the fan and induce an electric energy into the circuit.

Seems like either repaste and/or change slot or a usb to pwm adapter could do it.

Maybe a PCIe powered PWM card? There is surely some kind of that on AliExpress for cheap. You should probably have enough spare pcie slots to do it.

Seems like zfs or btrfs?
At least I usually read about storage file system usually being ZFS by default.

Well: A very quick phone research brought me to that forum post and page: https://community.hpe.com/t5/proliant-servers-ml-dl-sl/dl380-g8-fans/td-p/6273923/page/3?nobounce

Seems like the question of “anyone else?” was solved with: “Yes, had the issue with the P420 controller.” 9 years ago.
You could try to see if the comments on Page 2 and 3 are of any help.

Hope I could assist your issue at least a little bit.

What are the alternatives to it? NTFS? EXT4? ExFAT? FAT32??

What kind of card is it?
Depending if it’s on the PCIe riser or on the motherboard there are different possibilities.

Depending on how adventurous you are maybe repaste the heatsink?

For those without knowledge: Alternatives to BTRFS are what? EXT4 or NTFS?

In case of Germany: Take a look on eBay Kleinanzeigen
In case of not Germany: Local craigslist or whatever the equivalent to it is for you.