https://community.letsencrypt.org/t/shortening-the-lets-encrypt-chain-of-trust/201580/1

官方在2023年7月份发布了公告，

The summary is:

On 2024-02-08, we will stop providing the long chain by default, but clients can still be configured to request it.
可以尝试使用如下的参数，通过--preferred-chain手动指定根证书。

acme.sh --issue -d example.com --webroot /path/to/webroot --preferred-chain "DST Root CA X3"

但是，到了6月6日，手工指定也不生效了。
On 2024-06-06, we will stop providing the long chain at all.

9月30日后，DST根证书失效，用户使用过程中可能会面临问题。
On 2024-09-30, the cross-sign will expire, and any websites still serving it in their TLS handshakes may run into difficulties.