Looks like the ultimateretro photo is of v2.1 and that, to get the lower voltages, requires a VRM module, similar to the one necroware built and made a video about.
It's the connecter right of the cpu socket that looks like it's filled with jumpers.
The one on imgur seems to be v1.1 and has indeed a VRM onboard.

Yes, mine has v1.1 written on it and has empty spot where VRM is on the image from imgur. It seems that there were v1.1 with and without VRM installed

Well to put a conclusion to the story. Short story, I finally got LT1085CT voltage regulators and when I soldered it to the spot on the motherboard I can jumper between 5V (direct from PSU), 3.45V and 3.3V which are handled by regulator so board isn't limited only to 5V CPUs anymore.

Long story, at first I ordered LM338T voltage regulators. Rated for 5A so that should be enough. It took a while for them to arrive from China but for some reason they didn't actually work...

Instead of 3.3V I got 4.7V when I jumpered the board to use VRM instead of PSU 5V, some were even worse at 4.9V (I got 10 of them), marginally lower then direct from PSU... Adjustable "part" should be OK. I traced the circuit that leads to adjust pin on VRM and values of resistors there. According to formula it should output correct voltage.
And then I learned what LDO in LDO VRM means... Low Dropout... and LM338(T) isn't LDO and according to datasheet Vin - Vout needs to be at least 3V, here we have 5 - 3.3 which is definitely less than 3. Here's where LDO comes to play, they allow for smaller Vin - Vout difference, like 1.2 V or 1.5V and here our difference would be in spec...

But I wanted to test how they work anyway so I cobbled small circuit on breadboard where I fed 12 V into it and according to formula with resistors I used I should have got around 7 V on output which is bigger than 3V so it should be OK. But didn't, with some of the I got around 11.3V and others 11.8V...

Somehow I doubt they're all faulty, more probably they're simply fake components. Who knows what they actually are... Maybe some mosfets or something... I have to dig up component tester I have somewhere and see what it says they are.
Hazards of buying parts on aliexpress...

I also need some help to find a suitable Voltage Regulator please 🙏
Currently I am using the AMD 80mhz 5V but I would like to have the option for upgrading to a faster CPU 🙂

This is what you need:
https://www.ebay.com/itm/324723123533?

Majestyk : According to photos posted by previous commenter, what he requires is the same part as what the commenter before him, which happens to be the starter of this thread, used, an LT1085CT . So, no not that ebay part which might be usable on v2.x boards.

and maybe some cache chips.

Ahh thanks very much @weedeewee 🙂
So if I install the LT1085CT I should be able to use 3.3 & 3.45V CPUs immediately?

And don't worry this was long before I built up the system I have some cache installed