There is no change in the law. For at least 20 years, the law has been that if you donate a single item "or group of similar items" with a value over $5000, you must have a signed appraisal from a qualified appraiser (who also signs form 8283) and a signature from an financially responsible official at the charity who accepted the donation. The IRS does not give specific examples of what a "group of similar items" is. It may be discussed in their audit manuals or tax court cases, but I have not looked into it that deeply.
What changed is that Turbotax used to e-file returns with form 8283, with a requirement that the taxpayer mail the signed original to the IRS after e-filing. Turbotax no longer allows e-filing in that situation so you must mail your return.
Whether or not your particular donations constitute a "group of similar items" that requires an appraisal and signatures, is something you need to discuss with your personal tax advisor.
If audited (if you don't submit signatures), you have to convince the IRS that your donations are not part of a "group of similar items." I don't know where you are getting >$5000 worth of stuff to donate. But, if we suppose you are cleaning out someone's house after they passed away, for example, I don't think the IRS will accept splitting the donation over several days, to keep each day's worth under a particular limit -- that would probably be considered all one donation. Could you consider "clothes", "furniture", and "appliances" as separate "groups of similar items" and have each group under $5000 even though the total is more? I don't know. You may wish to ask a professional.
