I have a bike sepcifically set up for locking up, i use that bike whenever I'm planning on leaving the bike unattended in any area known to be frequented by third worlders and other thieving scum. It's a lovely bike to ride, I set all my bikes up well, it's old but the frame is top end steel tubing from the 90s, the group is all XT or DX etc, however it has been made to look like shit, I rarely wash it, the saddle while comfortable is tatty af, both wheels are bolted to the frame, no QR for the seatpost either, cables are mismatched as are the tyres and grips, the decals are in awful condition with some peeling away from the frame.
I don't want it to be stolen, I love it, riding it is actually a lot of fun because I really don't hold back, something liberating about not caring about chips and scratches etc, but if it ever is stolen I'll survive, it cost me like $200 so no drama. But to steal it would require effort, and because it looks so shitty to the untrained eye no theif will give it a second look anyway.
So that's the only bike I ever lock up, a simple chain and padlock through the frame, my other bikes are for bikepacking, trekking and cruising, situations where I am highly unlikely to leave the bike unattended at any point.
It's something I recommend al cyclists do, have one bike that is a cracking little rider but that has no emotional or sentimental hold over you, make it as unstealable and as visually unappealing as you can and take the stress out of mission trips into the infested city.