I don't know what the recommendation is in the US but I can tell you my experience here in France.
To go straight to your question about lumpy and hard scar tissue, my answer is "yes" and I am nearly 3 years after surgery.
A month after surgery, I had to go to a physio for massages. When the surgeon saw me again 4 months afterwards, he was quite upset because the massages were too gentle. So I had a new prescription that said massage the breast "actively and profoundly" like bread dough!!!
Then followed a year and a half of fierce and painful massages weekly and 20 sessions on a machine that is normally used for cosmetic purposes and which gives deep tissue massages.
I was told I had to wait 2 years before any reconstruction after radiotherapy finishes. I was due to go for my first operation mid April but Covid put paid to that and so I am now waiting for another date.
What he's proposed doing is to cut away the hard tissue, make 4 holes in my abdomen and do liposuction. The fat extracted is then put in a centrifuge to separate the blood from the fat. Then the fat will be injected into my breast. Apparently, according to how my body absorbs the fat, this might need to be done 2 or 3 times.
The lumpiness can be painful and, of course, the nipple has been displaced so that needs to be "straightened" out and the other breast lifted slightly so that I should have breasts that match in the end.
The surgeon has promised that the procedure will make the breast more comfortable as well as for aesthetic reasons.