I just built Tcl 8.6.11 for DOS.  See the links below [*] for details
and downloads.

Best regards,
-Ben

[1] Binary download link
https://archive.org/details/tcl-8.6.11-for-dos

[2] Upload link
http://www.ibiblio.org/pub/micro/pc-stuff/freedos/files/devel/tcl/

[3] Source download link
https://prdownloads.sourceforge.net/tcl/tcl8611-src.zip

[4] Changes

Summary of Changes since Tcl/Tk 8.6.10:
---------------------------------------
This is a patch release, so it primarily includes bug fixes and
corrections to erratic behavior. Highlighted changes are noted below.

* [TIP 581] disfavor Master/Slave terminology

* Revised handling of 4-byte UTF-8 sequences
*** POTENTIAL INCOMPATIBILITY ***

* Revised [binary (en|de)code base64] for RFC compliance and roundtrip
*** POTENTIAL INCOMPATIBILITY ***

* Tcl_DStringAppendElement # quoting precision, dstring-2.13,
dstring-3.10
*** POTENTIAL INCOMPATIBILITY ***

* Extended [clock scan] ISO format and time zone support
*** POTENTIAL INCOMPATIBILITY ***

* Revised case of [info loaded] module names
*** POTENTIAL INCOMPATIBILITY ***

* [info hostname] reports DNS name, not NetBIOS name
*** POTENTIAL INCOMPATIBILITY ***

* Force -eofchar \032 when evaluating library scripts
*** POTENTIAL INCOMPATIBILITY ***

* Revised error messages: "too few" => "not enough"
*** POTENTIAL INCOMPATIBILITY ***

* Fix crashes or hangs in...
- [lsort [lrepeat 89478486 {}]]
- errors in parser initialization

* Fix memory issues...
- proper ref counts for failed [superclass], oo-1.18.[45]
- index input validation for Tcl_Get(Range|UniChar)
- checking for trailing / on an empty path
- revise extensible structs to make more compiler checks happy

* Repair regressions in...
- \U1E2165 and \U10E2165 parsing stops, utf-10.[67]
- [string match \[a\u0000 a\x80] should return 0, util-5.52
- [string trim $invalid-utf-8], string-20.[78]

* Rewrite of zlib inflation for multi-stream and completeness

* Run fileevents in proper thread after [thread::attach $channel]

* Prevent cycle in command resolution, namespace-57.0

* Proper rejection of overlong sequences by Tcl_UtfPrev, utf-7.(24-46)

* Fix auto_path initialization by Safe Base interps

* Fix [expr 1e2147483648] to not return 0.0

* Stop [unload] corruption of list of loaded packages

* Fix errno management in socket full close

* Encoding tis-620 failed to load

* Support for Unicode 13

* tzdata updated to Olson's tzdata2020e