Well, I'm glad to know that I'm not alone with this. Since upgrading to Big Sur a week or two ago, I am seeing "Service Recommended" and that my "battery's capacity is significantly reduced". I have noticed that I am needing to charge it much more frequently, as well. Unlike others that have commented, mine is still working fine when it is plugged in, thankfully. MacBook Pro (Retina, 13-inch, Early 2015) Processor 2.7 GHz Dual-Core Intel Core i5 Memory 8 GB 1867 MHz DDR3