My digital microscope has no lag and brilliant resolution. You can easily solder under it just looking at the screen. Just don't get the super cheap ones but one for maybe 150€ or so.

Yeah you can get an old Bauch&Lomb for under $200. Probably need an LED illuminator ring for $10 too.

They have great field of view (cm) at decent/variable magnification (20-100x) and response time is instant, whereas your phone/USB are going to have just enough delay to be annoying.

I have a USB microscope and I'd say my phone on 5x soft-zoom is a pretty similar experience. The main thing is having enough screen size you can see, and a stable platform.

Plus USB scope things are like $80 on AliExpress and work fine.

Can you recommend a macro lens to use?

As much as I'd love to try your suggestions, they're very expensive even in that space.

From what I can see, the Mantis microscopes are in the $3500+ range and the JBC stuff is similarly expensive.

Most hobbyists would cringe at the price of buying a Thermaltronics soldering iron and that's like 5x cheaper. However, I can at least conclusively demonstrate the vast difference between something like that and a Hakko right in front of a person.

This stuff is like the difference between a $100 guitar, a $500 guitar, and a $2000 guitar. The difference between the $100 and the $500 one is obvious to almost everybody. The differences between the $500 and $2000 one won't be obviously noticeable until you get a lot of experience.

My mother was recently cataloging some very small pots from an archaeological dig. I sent her with my nice camera, a prime lens, some macro adapters, and an adapter that would let her mount the body to the eyepiece of a microscope. The detail she was able to capture with the prime and macro adapters so vastly exceeded the capabilities of the university microscope that she decided to just use the camera, which had the additional advantage of having focus stacking to compensate for the shallow depth of field.

I would expect that this setup would work pretty well for a bench microscope setup if the camera can output video and isn't too big to mount on a tabletop tripod. Rather a lot can be done with crop zoom if you can get the focal length and lighting right.

In a pinch, but you have to get your nose way too close to the soldering iron.

I stumped up for a set of dental loupes many moons ago and they were nice, but expensive. They're safety glasses to boot.

They're come down dramatically in price since then. https://www.practicon.com/Loupes-Magnifying-Eyewear