If you don't want to mess with capacitors then absolutely stay away from ABit. I love ABit boards, they are iconic enthusiast motherboards with detailed BIOS features, but in that time period they all have bad caps. This is why they went out of business.
The Gigabyte boards I've seen in that period also had bad caps, but maybe not as bad as ABit's. I'd avoid them, though.
AOpen, Asus, and Intel had good capacitors in the 440BX Slot-1 era.
Probably Tyan and Supermicro, but I'm not sure about them.
I have a mainstream Tyan socket-7 board from ~1998-99 and I think it had a mix of mostly Sanyo caps (good) but also some that were cheap.
I've seen some bad caps on later Supermicro boards but I don't know about the late 90s.
Most manufacturers had bad caps unfortunately.
There might be a strong supply of Intel SE440BX-2 or similar model boards available, maybe at decent prices. Around maybe 10 years ago a warehouse in the US sold thousands of them as new old stock. There's probably a lot of them in resale nowadays, maybe some got over to Europe.
These are very conservative boards with limited options (made by Intel, after all), but they are very reliable.
Intel's Slot-1 boards were also used in Dell computers. You might find more of the Dell version than the Intel version. The Dell version will have a Dell logo on it, the Intel version will have an Intel logo. The Intel version works with a standard ATX power supply and that's the one you probably want.
The Dell branded versions of these boards require a different power supply, or an adapter. You might find a good bargain on these boards because most people avoid them, but if you don't want to deal with the power supply issue, don't get a Dell branded board.
If your friend is looking for a P3 at 450-600MHz, then it sounds like he's looking for a Katmai CPU (which runs on the same 2.0V that previous Pentium 2 does). There are some Coppermine CPUs in that clock range which are faster, but they use a lower voltage and you have to pay attention to whether the motherboard supports them.
Many 440BX motherboards can run Coppermines without actually saying they do in their documentation, so follow up with that if you need help with it.
This applies to the Asus P2B - many of them have Coppermine support prior to when it became official.