I'm fortunate to have three 2x12" combo amps with optional RF bypass loop alternate input, but I also use my loopers with everything from my smaller Blackstar ID:Core 40 practice amp which doesn't -very similar in concept & execution to the Katana 50, my Fender Acoustasonic acoustic guitar amp, and even my Blackstar Fly 3s.

Sounds "OK" is one of those individual perception judgements. Electronically, no it's not "optimal". But front instrument input still gets the job done & sounds good enough for looper practice purposes to my undoubtedly age affected presbycusis hearing. As practice should be clean most of the time in any case to avoid obscuring mistakes (ref: Chris S & Hele I), it's really moot for my purpose on those smaller amps. It's not like a Chorus or Delay pedal won't work without bypass, or necessarily even sound 'bad'. But people are strange cattle hearing what they want to hear much of the time as becomes evident in the endless tube vs digital tube emulation arguments.

Just for the sake of exmple, here is a tiny Blackstar Fly 3 taking pedals through the instrument input. More than acceptable [u]in its role[/u] I'd say. It's not like it'd be used for anything else in the way of 'performance' but playing to family or friends at home or busking on an [u]ultra[/u] tight budget?

If I were using a looper in support or effects pedals, of which I have quite a few, for professional public gigging performances or recording to that same end -I don't, and on a much louder amp it might become a consideration, but in my home studio? I do this for enjoyment. Pragmatism & convenience overrule perfection/optimal deployed to my primary purpose. Appreciate Y&OMMV.