While creating a bridge, documentation is not clear (and I would say that it should explicitly state this) on IP assignment of the NIC.
In my confing, my NIC already had fixed IP address (I have multiple NICs), I have created bridge according to the documentation for which I choose DHCP for IP address assignment.
When bridge was created it correctly took IP address from DHCP, but my communication to the truenas on that NIC failed (it was not accessible at all on my NIC/bridge, including ping - funnily, I could access my VMs and they could go out but could not access truenas host and/or bridge).
The problem is/was that both my NIC and bridge had assigned IP addresses and when I removed address from my NIC it all started working nicely again.
So I strongly suggest clarification in documentation (including correction to the screenshot of NICs with Bridge where Bridge is not visible at all :).
Here how it looks for me now (when everything works ok):
While documentation failed to clarify this, I found this solution on reddit (so thanks to whoever wrote that), I post this here for future reference for someone who might loose an hour or so to figure out what and why went wrong:
https://www.reddit.com/r/truenas/comments/rjee50/scale_i_am_lost_with_a_bridge_setup_help/
p.s. in other news: while I do understand rationale for not allowing multiple DHCP assignments on NICs, I also think that people who run Truenas should be able to understand and use DHCP effectively and correctly (I for example think that my IP across all network segments should be configured/done from my DHCP server regardless of the role of connected device)
p.p.s. on my networking equipment it is perfectly possible to have both bridge and associated NICs within the bridge to each have its own IP address within same subnet - so this is why it was confusing for me