@steen you've already had several threads around your problems getting zerotier to install on various low-flash devices. You have yet to confirm that a device with 8 MB of flash is sufficient or that 64 MB of memory is sufficient for it to run reliably. I'd strongly suggest you consider 16 MB of flash and 128 MB of RAM as a minimum.
For a couple dollars (or whatever your local currency is) more, a decent device in the same price range will save you time over the cheapest ones out there and likely be upgradable for much longer than one that is still RAM constrained, even if it has the marginal 8 MB of flash.
Your best resource for inexpensive devices continues to be