Any recommendations regarding Imperialism definitions?

Hey, I'm currently trying to educate myself more on imperialism. Around here I’ve mostly been confronted to Lenin’s definition as it appears in his famous book "Imperialism, the Newest Stage of Capitalism". In other circles IRL, I’ve heard people refer to Luxemburg definition which appears in "The Accumulation of Capital: A Contribution to an Economic Explanation of Imperialism".

I’ve read both books and I’m still a bit lost. I can see points for both definitions. I can also see some divergences. For example using Lenin’s definition I cannot see how Russia could be seen as an imperialist country right now. However, with Luxemburg’s one I feel they could be included as an imperialist country. Of course in much lesser proportions as the hegemonic imperialism that that are the US.

I’m looking for modern resources that either actualize and synthetize both definitions or resources that debate this very subject (ie various marxist definitions of imperialism) so that I can get a better grip/understanding on it.