I have been getting treatment for lymphodema in the breast. Swimming (thanks folks here for recommending that!) and mobiderm have been the most helpful so far for getting fluid down. not sure if folk are familiar with mobiderm - a lymphodema physio gave me a small piece to put in my bra — it’s uneven surface like bubble wrap seems to help fluid to move around. I liked the result so well that I have purchased some from the mobiderm.com.au site.
https://mobiderm.com.au/collections/mobiderm-bandage-system - I prefer the 5mm x 5mm stuff but accidentally ordered the 15mm x 15mm, which seems to work ok too, just lumpier. I have also bought several different bras but anything very compressive seems to set the swelling off. I have been recommended someone to try who specialises in fitting bras for lymphodema so I’ll give that a go too. Not sure if others have had good results with mobiderm or not.