Hello Jam and welcome to the forum.

We both use very old Bernina sewing machines for free style embroidery.

I have a Bernina 801 and Annie uses the Bernina 801 Sport. We like the old machines because they are solid metal, easy to maintain and seem to be able to go for longer stints than their modern counterparts (we deduced that from our attendance at several workshops where there were many different machines being used for the same purpose).

The old machines are also uncomplicated by computer wizardry etc - all you need for free motion embroidery is straight and zig-zag stitch.

Make sure the machine you choose has feed-dogs that can be lowered.
(Some machines have a little plate to cover the dogs, but it really gets in the way and is no good.)

I've got a Bernina 1008 which is great for free motion embroidery but doesn't do anything fancy. Although I've only had mine about 18 months they do go on for over 30 years. However if you want to do lettering you really need a computerised one, Bernina make them but never used one myself.