I have this TextFormField:

    TextFormField(
      key: const ValueKey('lastname'),
      focusNode: _lastnameFocusNode,
      controller: _lastnameController,
      style: const TextStyle(fontSize: Sizes.twenty),
      decoration: InputDecoration(
        suffixIcon: _showLastnameSuffix
            ? IconButton(
                icon: const Icon(
                  Icons.close_rounded,
                  color: Colors.grey,
                ),
                onPressed: () {
                  _lastnameController.clear();
                  setState(() {
                    _showLastnameSuffix = false;
                  });
                },
              )
            : null,
        border: _myOutlineInputBorder(),
        hintText: tr(context).lastname,
      ),
      inputFormatters: [
        FilteringTextInputFormatter.allow(RegExp(r'[A-Za-zs]')),
      ],
      textInputAction: TextInputAction.done,
      onFieldSubmitted: (_) {
        FocusScope.of(context).unfocus();
      },
      minLines: 1,
      maxLines: 1,
      onChanged: (value) {
        setState(() {
          _showLastnameSuffix = value.isNotEmpty;
        });
      },
    );
  }

I have alsoe a firstname Texfield which basically built the same with textInputAction: TextInputAction.next.
When I switch from firstname field to lastname field the keyboard action remains next until I enter some characters and only then it switches to done.
Same thing when I go from lastname to firstname. The keyboard action remains done until I enter some input and only then it switches to next.

It happens only on physical device (Samsung S20). Emulator in android studio reacts as expected.