The 60.4g one is here. It has a 2.45 inch screen, 1100mah removable battery, has been around for a while, and runs Android 8.1. By its dimensions it MIGHT fit into an Altoids tin (which would of course block RF signals from reaching it, good or bad depending). I emailed the company and they replied there are no plans to update it, unfortunately. They have a newer "Jelly Star" version that runs Android 13 and has more features, but is 2x as heavy. I suspect the lighter one didn't catch on because the battery was too small, but it might be ok if you don't actually use the phone much.
The 560g version is here. It is that heavy because it has a 22000mah(!) non-removable battery. It also has a built-in 1200 lumen flashlight, 6.81" screen, accepts 65 watts USB PD fast charge, and generally looks like a capable modern (8gb ram, Android 12) phone, though it is 4g only. They do have some 5g models that are smaller.
Why is a 560g phone ultralight? Well on Reddit r/ultralight they always talk about power banks, and the lightest 20000mah power bank is around 300g and it is popular there. This thing combines the power bank and a phone, so saves the weight of a separate phone. They also like to spend days on the trail and then duck into a restaurant for a recharge, so they like fast charging. Most phones and power banks recharge at 15 watts so you don't get that much in an hour, even with separate chargers for your phone and PB (i.e. 30 watts using both at once). This thing supposedly takes an almost full charge in under 2 hours. Finally, it is good to get rid of the cable between the power bank and the phone. Not for weight (you still need to bring a cable) but because USB connectors are way too fiddly and they break all the time. So the less often you plug and unplug a phone, the better. Huge batteries from that perspective are good.
I should also mention, the above is supposedly a ruggedized phone. If that means you don't need an add-on protective case, that saves some more weight.
I have never used or seen either of these phones (just heard about them last night) and don't feel likely to buy one (especially the Tank), but both are interesting enough that I thought I'd post here.
Update: there is an even bigger (666g, 31mm thick) follow-on with Android 13, 5G radio, 16GB ram, and 120 watt charging: https://liliputing.com/unihertz-tank-3-smartphone-has-a-23800-mah-battery/
The larger phone lists more frequencies, but I didn't exhaustively research if it has the right bands to get good overlap with US carriers.
If you can, 5G is the way to go. There is no new development on 4G and few to no new 4G towers are being installed at this point. Coverage on 4G will only get worse over time, and 5G coverage is already better in most parts of the country. It'll be the same story with 4G in a few years as it already is with 3G which is now useless or nearly useless as carriers are not widely supporting it anymore and some carriers having already dropped it entirely.
Thanks! I picked up the 5G Motorola yesterday. Had to uninstall a lot of bloatware and unset a lot of privacy invasion switches, but I do like the phone.