You are describing citizenship. Most countries allow long term residence (>3 months) with lower requirements. It’s often easiest to look for work first, if you are competitively skilled, or are looking somewhere with labour shortages, as sponsorship makes it easier.
The Baltics are in a much stronger position than Ukraine. They are in Nato already, and are geographically important as a buffer to the only Nato members who actually take Russia as a serious threat (Norway, Sweden, Finland and Poland.) Tactically, air and sea defence of the Baltics is externally feasible, and the Baltics nations have focused on building land defense over the recent years. If you combine this with the obvious Russian war fatigue, and lack of resources, it is clear the Russia doesn’t have the capacity to invade the Baltics over the next two years at least, even if the Belarusians participated.
All of this becomes even harder if the Russians are gifted Ukraine and have to occupy it militarily.