The claim that Putin just attacked Denmark, Sweden, and Norway with drones as preparation for an invasion is mostly false because while there have been confirmed Russian drone attacks over Poland and increased military provocations near Nordic countries, there is no verified evidence of direct drone attacks on Denmark, Sweden, or Norway or an imminent invasion plan against them.
Putin just attacked Denmark, Sweden, and Norway with drones. This is preparation for an invasion

How are Nordic countries Sweden, Finland, Norway, and Denmark preparing for potential war amid Russia-Ukraine conflict? - The Times of India
Source: timesofindia.indiatimes.com
Key Evidence
Multiple sources confirm Russian drone attacks over Poland but not over Denmark, Sweden, or Norway.
abc.net.auabc.net.auPoland drone attack shows Putin has no peace plans any time soon
politico.eupolitico.euPutin tests NATO with drone assault on Poland+1 more
Nordic countries are increasing civil and military preparedness amid regional tensions but have not reported being attacked by drones.
timesofindia.indiatimes.comtimesofindia.indiatimes.comHow are Nordic countries Sweden, Finland, Norway, and Denmark preparing for...
bbc.combbc.comSweden, Finland and Norway release new advice on surviving war+1 more
Interceptions of Russian military aircraft near the Baltic Sea have occurred but do not equate to drone attacks or invasions.
dailymail.co.ukdailymail.co.ukMoment NATO jets intercept Russian SU-30 warplanes carrying supersonic missiles...
npr.orgnpr.orgGerman and Swedish jets intercept Russian military plane over Baltic Sea : NPR
What the Evidence Shows
Recent credible sources confirm that Russia has conducted drone attacks over Poland, which NATO and European experts interpret as aggressive signals or tests of NATO's defenses.abc.net.auabc.net.auPoland drone attack shows Putin has no peace plans any time soon However, there is no verified report from reliable news outlets or official statements confirming that Russia has launched drone attacks specifically targeting Denmark, Sweden, or Norway. Instead, these Nordic countries are actively preparing for potential crises amid the Russia-Ukraine conflict by increasing civil defense measures and military readiness.
timesofindia.indiatimes.comtimesofindia.indiatimes.comHow are Nordic countries Sweden, Finland, Norway, and Denmark preparing for...+5 more
Military encounters such as Russian warplanes being intercepted over the Baltic Sea near Sweden and NATO airspace violations have been reported, but these are not drone attacks and do not constitute direct assaults. The heightened tensions and military posturing in the region reflect ongoing strategic rivalry rather than confirmed acts of war against these Nordic states.npr.orgnpr.orgGerman and Swedish jets intercept Russian military plane over Baltic Sea : NPR
dailymail.co.ukdailymail.co.ukMoment NATO jets intercept Russian SU-30 warplanes carrying supersonic missiles...
Regarding the claim that these actions are preparation for an invasion, historical context from the Russian invasion of Ukraine shows that large-scale invasions were preceded by massing troops and equipment near borders.en.wikipedia.orgen.wikipedia.orgPrelude to the Russian invasion of Ukraine Current evidence does not indicate similar mobilization or direct attacks on Denmark, Sweden, or Norway. Thus, while the situation is tense and Nordic countries are preparing defensively, the specific claim of drone attacks on these three countries as a prelude to invasion lacks substantiation.