Offshore tax havens is the usual one. Panama papers put only a small dent in that. All sorts of stuff that's been cracked down on in recent years, like "take your salary through a one person company as dividends".
UK had a scheme where people would take out ""loans"" from their employer that would then be "forgiven". I believe this one blew up Rangers football club.
Fun UK example from the 70s: the tax on car parts was much lower than the luxury tax on cars, so people invented the "kit car" which you assembled yourself: the Caterham 7. Still niche popularity today.
Well, for one, people who owned small/medium sized businesses would put effectively their entire family on payroll to cut the businesses’ earnings and lower their tax bill.
Don't forget that it also had the highest level of tax dodging available through various mechanisms.
If you think the lengths people go to now are extreme to avoid taxes-- think about what they did were willing to do then.