Can we fix these sentences while here?

A value of 1 indicates that the device is a solid state disk, i.e., non-rotational.
The default value is 0.

For true consistency we actually need to standardize it the other way, the interface has been externally called fw_cfg since even before we got it, right?

https://www.qemu.org/docs/master/specs/fw_cfg.html

In the roff language, new sentences start on newlines. You can check the linter with mandoc -Tlint /here/is/the/manual.

That said, I would suggest a more active voice here, for this sentence, something like:

Only one active connection is allowed at any time.
The TCP server will immediately close new connections while an existing connection is active.

This is the formatting consistently used in the NVMe 1.4b specification.

Using this syntax is fine, but I don't think it is ambiguous to use plain GB here and elsewhere. Memory sizing is always power-of-2, so memory/RAM sizes and address space sizes (e.g. the 64K window for VGA) are always power-of-2. (This is different from some other places like disk sizes where it is indeed ambiguous.)

In particular, the syntax accepted for the command line doesn't accept the i, only GB or G (see expand_number(3)).

I didn't change any or the options, put only free form prose.