Sorry but I don't quite understand what you mean. Let's Encrypt does not have a "Sandbox" although it has a Staging system for test certs. Is that what you mean?
I just got a cert from Staging and Production and the chains look the same to me. Except of course that the Staging certs are not publicly trusted.
# STAGING (shortlived profile)
subject=
issuer=C=US, O=Let's Encrypt, CN=(STAGING) Artificial Amaranth YE1
subject=C=US, O=Let's Encrypt, CN=(STAGING) Artificial Amaranth YE1
issuer=C=US, O=ISRG, CN=(STAGING) Yearning Yucca Root YE
subject=C=US, O=ISRG, CN=(STAGING) Yearning Yucca Root YE
issuer=C=US, O=(STAGING) Internet Security Research Group, CN=(STAGING) Bogus Broccoli X2
subject=C=US, O=(STAGING) Internet Security Research Group, CN=(STAGING) Bogus Broccoli X2
issuer=C=US, O=(STAGING) Internet Security Research Group, CN=(STAGING) Pretend Pear X1
# PRODUCTION (shortlived profile)
subject=
issuer=C=US, O=Let's Encrypt, CN=YE1
subject=C=US, O=Let's Encrypt, CN=YE1
issuer=C=US, O=ISRG, CN=Root YE
subject=C=US, O=ISRG, CN=Root YE
issuer=C=US, O=Internet Security Research Group, CN=ISRG Root X2
subject=C=US, O=Internet Security Research Group, CN=ISRG Root X2
issuer=C=US, O=Internet Security Research Group, CN=ISRG Root X1