What are people liking for audio interfaces? I have an ancient and cheap-at-the-time Edirol UA-4FX that seems not to want to play nice with the Arturia KeyStep and if spending the money on a new interface would fix the problem (but who knows?) I’d rather do that than return the KeyStep.
Of course I’m one of those people who insists on running Linux, so that complicates things, but it can usually be worked out.
How many ins and outs are you looking for?
Mainly it’d be used just to record one instrument. One instrument plus one mic would be nicer but not essential.
I got a Zoom R16 explicitly to use as a multi-tracker for jams, but have actually ended up exclusively using it as an audio interface almost by accident. It has 8 Neutrik inputs with phantom available on 5&6 (and as the name suggests records 16 channels/tracks) so it might be a bit much for your needs, but for what I paid it’s a great value. Channels 7 and 8 can be either their lines in or built-in microphones. It is a light plastic though-if I were a gigging musician I wouldn’t want to take it to a venue where people were eating/drinking.
I have a small and cheap mixer with usb (xenyx q802usb 70€) and it just works in my Ubuntu. Build quality is not great, I can not say anything about sound. I wanted cheap 
Scarlett 2i2 is designed and marketed for instrument and microphone. The going rate for one of those second hand on eBay seems to be about £80. It’s a good, solid bit of kit. It gets its power from the USB bus so I pair it with an Amazon Basics powered hub which I also use to switch the theremin, the MidiSport DIN MIDI converter and two or three other items.
https://focusrite.com/en/usb-audio-interface/scarlett/scarlett-2i2
I’m afraid. No, it won’t.
I’ve been using a Behringer UMC404HD, which is good quality, and includes an extra midi interface.
But I long back to the days that I had my PCI-express delta 1010 interface in my WinXP-music machine which had a serial interface so that it could control my unitor 8 and had no USB noises whatsoever.
I had been making music with logic 5.5 for PC for longer than I can remember until that horrible Saturday when the 15 - 20 year old PC refused to start up and I saw that at least half of the capacitors on the motherboard was leaking.
Thats exactly what i use. No fuss inexpensive lots of features. that many inputs/outputs and midi i/o. Latency is good, not much else you could want for something that price. Hell, i dont need more.
I know better than to suggest a Behringer interface to @analogoutput, though I also use two of their big ones. I’d say the Focusrite, Tascam or Native Instruments ones are good bets. Don’t know about Linux support, though, as my Unix comes wrapped in an Apple box.
EMU 0404USB… Got it for £30 S/H on ebay but have hardly had a chance to use it since getting it and having stuff all over the place in life due to Corona…
It worked out of the box on Linux … Little more tricky on W10 due to it being an old device…
Did solve getting SYSEX dumps to the Korg M1 I had, which would not work on a cheap USB/MIDI…
There’s nothing wrong with Linux, after all… it does do a good impersonation of Unix, and imitation is the highest form of praise. When I do play with a friend, I use his old Moog and an old mixing unit cobbled together with my iPad. It can be chaotic, as we’re both controlling it. He uses a soft synth on his PC, my iPad handles the delay / echo / bit crush effects. It’s fun!
I have been using linux for 24+ years both for server infrastructure for all sorts, and as my main home O/S for probably 16 years… But the Linux audio whilst very versatile and powerful, is a mess, and the available DAWs are quite under developed.
I did admin and networking with Solaris, on Sun Sparc hardware mostly + Oracle, but did get enthusiastic about Linux enough to convince the guys I worked for to invest in it. Have never done audio with Linux though. Shame about that, the rest of it seems to be ok.
Yes, this is my pain.
Also a Long-time Linux User here 
in recent months I am learning a lot of FreeBSD though! Especially zfs and jails are great!
I used to like different flavours of *nixes, we had HPUX, Sco, Sunos, Solaris , Linux and a MicroVax running a *nix. I learned the craft on that MicrovaxII. Ahhhh rose tinted glasses time…
just saw this today . I had the delta 1010 , loved it . using a focusrite pro 14 [ fire wire ] and yeah there was a lot less noise with the 1010 .